Pulmonary Embolism USMLE Step 1 Practice Question
A 34-year-old woman is admitted to the hospital after sustaining a displaced right femoral fracture in a motor vehicle accident. She undergoes open reduction and internal fixation with intramedullary nailing. On postoperative day 2, she develops acute dyspnea, tachycardia, and hypoxemia. Vital signs show: temperature 38.2°C (100.8°F), heart rate 118/min, respiratory rate 29/min, blood pressure 148/88 mm Hg, and O₂ saturation 84% on room air. Physical examination reveals scattered petechiae across the anterior chest wall and confusion (disoriented to time and place). Laboratory studies show hemoglobin 10.1 g/dL, platelets 135,000/mm³, and creatinine 1.3 mg/dL (baseline 0.9 mg/dL). Chest X-ray reveals scattered opacities bilaterally. Which of the following best explains the pathophysiology of this patient's acute presentation?
Answer choices
- AThromboembolism from deep venous thrombosis in the fractured limb
- BFat embolism syndrome from disruption of bone marrow during fracture and surgical fixationCorrect answer
- CAcute respiratory distress syndrome secondary to systemic inflammatory response from trauma
- DSeptic pulmonary embolism from hematogenous seeding of bacteria at the surgical site
- EAcute coronary syndrome with subsequent acute pulmonary edema
- FAspiration pneumonia with associated acute hypoxemic respiratory failure
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